Sample Entry: how to read these reference pages — Availability: Inherits from

Title and Short Description

Every reference entry begins with a four-part title block like that above. The entries are alphabetized by title. The short description, shown below the title, gives you a quick summary of the item documented in the entry; it can help you quickly decide if you’re interested in reading the rest of the page.


The availability information is shown in the upper-right corner of the title block. In earlier versions of this book, this information told you what version of what web browsers supported the item being documented. Today, most browsers support most of the items documented in this book, and this availability section is more likely to tell you what standard provides the formal specification for the item. You might see “ECMAScript v1” or “DOM Level 2 HTML” here, for example. If the item has been deprecated, that is noted here, as well.

Browser names and version numbers do sometimes appear here, typically when the item being documented is a cutting-edge feature that is not universally adopted or when the item is an Internet Explorer-specific feature.

If an item, such as the History object, has never been standardized but is well supported in browsers that support a particular version of JavaScript, then this section may list that JavaScript version number. The History object, for example, has an availability of “JavaScript 1.0”.

If the entry for a method does not include ...

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